This invention relates to a mass spectrometer and process of using same capable of measuring both energy and mass of daughter ions formed by dissociation or fragmentation of parent ions.
It is known that the measurement of ion dissociations or ion fragmentations is effective for analyzing constitutive property of organic compounds or organic mixtures. In the conventional apparatus for measuring ion dissociations or ion fragmentations, ions produced and accelerated by an ion source are selected according to their mass to charge ratio by a first field such as a magnetic field or double-focussing field. The mass-selected parent ions, which have a desired m/e ratio, are directed to a collision chamber in a field-free region and collide with inert gas, such as helium gas, supplied in the chamber, thereby a part of the parent ions forming daughter ions. The daughter ions are also formed in the field-free region without the collision chamber by the self fragmentation reaction of the parent ion. The daughter ions are directed to a second field such as an electric field or double-focussing field. In the case of using the electric field as the second field, the daughter ions can be precisely selected according to their kinetic energy. However, spectrum width of the kinetic energy of any daughter ion is broad, since a part of internal energy of the parent ion is released at the dissociation. Therefore, the mass of the daughter ion cannot be measured at high resolution.
In the case of using the double-focussing field as the second field, the mass spectrum of the daughter ions can be obtained at high resolution, since the daughter ions are double-focussed by the field. However, the daughter ions having various kinetic energies are focussed on an ion collector at the same time under certain field conditions if these daughter ions have same mass. Therefore, the kinetic energy spectrum of the daughter ions cannot be obtained in this case.